Could I ask you to experiment with trying this with the Bright.itmz and pastel.itm templates in the .zip, to see if they are making a difference on your system ?

(I take it that the script is not reporting failure to find the template ?)

The script does two things with the template:
1. it adopts the plist wrapping of the data
2. it reads the colours just from the top level branches

It may be worth studying the two supplied examples in a text editor (you'll need to unzip the .itmz file and look at the map.itm file which it contains) and comparing them with the template you are using.